Firefly is the given. It had great potential but was sunk by executive meddling.
More recently, Dark Matter was left hanging after three seasons.
I haven’t (yet) seen a vote for The Expanse, which IMO is the best SF series of the last ten years. Supposedly Amazon picked it up after SyFy canceled it, but the fourth season has yet to materialize. I’d hate to think it fizzled out mid-story.
I need to watch that.
However I am always leery of moving law enforcement stories into space. The hardly ever work right.